bool_in bool_out pg_date_in pg_date_out pg_interval_cmp pg_interval_in pg_interval_make pg_interval_mul pg_interval_out pg_interval_pl pg_time_in pg_time_out pg_timestamp_in pg_timestamp_mi pg_timestamp_mi_interval pg_timestamp_out pg_timestamp_pl_interval pg_timestamptz_in pg_timestamptz_out

pg_interval_pl() Interval * pg_interval_pl ( const Interval *  span1, const Interval *  span2  ) Add an interval to a timestamp data type. Note PostgreSQL function: Datum interval_pl(PG_FUNCTION_ARGS)